The present invention relates to a method and apparatus for starting spinning on an open-end spinning apparatus, generally of the type having a feed device for supplying a sliver to an opening roller received in a housing and from which separated fibers are supplied via a feed channel, by means of a suction-air stream, to a fiber-collecting surface for thread formation. Generally in accordance with this invention, at the start of spinning, a thread end is returned to the fiber-collecting surface, from which the previously returned thread is then drawn off again, with fibers being continuously tied in thereto. Further to prepare for the start of spinning, the feed device is switched on and while running, the fiber stream on its way to the fiber-collecting surface is deflected therefrom and instead at least partially supplied to a sucking-off device.
In conventional devices, when a thread breaks or the spinning process has stopped for any other reason, the feed device is stopped immediately to prevent unnecessary supply of fibers which clog and could otherwise damage the spinning apparatus. However, the opening roller usually continues to run, since stopping of such roller requires high technical precision (especially for each separate spinning station), and starting up and running down requires a considerable amount of time. As a result, the fiber tuft projecting into the region of the opening roller from the stopped feed device is stripped off completely. Before the spinning apparatus can be restarted, these fiber residues first have to be removed from the fiber-collecting surface. Such removal is required because these shortened and therefore damaged fibers sometimes prevent the spinning process from continuing satisfactorily. The issue of such phenomenen is raised in Swiss Patent Specification No. 526,646.
It is therefore known from the conventional practice of starting spinning and eliminating a thread break by hand that a spinner (an individual who operates a spinning apparatus) first operates the feed device for a short time, then cleans the spinning apparatus, and only after accomplishing that, pieces up the thread. Such activity, known as prefeed, removes the damaged part of the fiber tuft with the shortened fibers.
Even though a considerable number of the fibers are damaged by subsequent stoppage of the feed device during cleaning, sufficient fibers remain in the fiber tuft for spinning to start successfully. Stoppage of the feed device, dependent on the time required for cleaning, usually produced about the same fiber tuft conditions for the start of spinning. Hence, the success rate for piecing up thread was considerably improved with the above-mentioned prefeed technique, even at high rotor speeds and with difficult materials.
Knowing that damage to the fiber tuft is a function of the length of each stoppage of the feed device, it has been previously proposed to continue running the feed device, and then deflect and guide the fiber stream on its way to the fiber-collecting surface past same and instead into a sucking-off device. For this purpose, sucking-off orifices (such as disclosed by British Patent Specification No. 1,170,869) or compressed-air orifices (such as disclosed by German Patent Specification No. 3,104,444, which is equivalent to U.S. Pat. No. 4,384,451) are provided in the feed channel.
Even though, as a result of the uninterrupted fiber-feed and opening operation, undamaged fibers are supplied to the fiber-collecting surface exactly at a desired time, the spinning process is still disturbed by orifices of such type in a highly sensitive fiber transport path between the opening roller and the fiber-collecting surface. Hence, none of such prior proposals provide a practical solution for the above recognized and described technical problem.